strange artifacts

Hi all!

I'm experiencing a strange problem:

I'm exporting the model of a curved glass with vertex normals
to obj and converting it into a radiance mesh.
I'm using the dielectric material with it, so the glass object has two
surfaces (inner and outer side of glass), but I can't get rid of this
strange effects at the edges, where the quads become triangles.

The remaining part of the surface is fine, even at the center,
where there are some other triangles. I need to subdivide the polygons
many time before this effect becomes less noticeable ...

Any ideas?

Thanks!

···

--
Francesco

Hi Francesco,

This could be a problem with obj2mesh, though at first glance I can't spot anything wrong with the code. Is it possible that whatever software is generating the OBJ is being clever and not including surface normals on the flat quad vertices? Say it was including surface normals on the vertices next to the edge, where it needs them, but not on the interior vertices, which should match the geometric surface normals. In such a case, I could understand why obj2mesh would screw up as it converted quads to triangles, some of which would have surface normals and others which wouldn't. Where such triangles shared an edge, you would end up with inconsistent output like this.

It may be fixable, but I need to get a copy of your OBJ file to study it. Send it to me gzip'ped in a separate e-mail. (No need to copy the group.)

-Greg

P.S. Out of curiosity, do you get the same results from obj2rad?

···

From: Francesco Anselmo <[email protected]>
Date: June 27, 2005 7:37:08 PM BDT

Hi all!

I'm experiencing a strange problem:
http://www.bozzograo.net/radiance/pub/artifacts.jpg

I'm exporting the model of a curved glass with vertex normals
to obj and converting it into a radiance mesh.
I'm using the dielectric material with it, so the glass object has two
surfaces (inner and outer side of glass), but I can't get rid of this
strange effects at the edges, where the quads become triangles.

The remaining part of the surface is fine, even at the center,
where there are some other triangles. I need to subdivide the polygons
many time before this effect becomes less noticeable ...

Any ideas?

Thanks!
--
Francesco